A friend of mine uses a lot of sarcasm. When confronted with this as being kind of nasty, he says, “Lighten up! It was only a joke.” I think he harbors deep anger within him. What do you think?
If this is a pattern and if he sees that others are hurt (which you imply that he does), then, yes, I suspect the same: hidden (from him) and deep anger. He may need to courageously explore who has hurt him in the past and try to practice forgiving, if he chooses. It might lessen or even eliminate his hurtful sarcasm.